Various available simulators provide transients for determining endurance of automobile electronic devices such as radios, engine controllers, information displays, etc. One simulator generates a very fast rise time 80 volt, 22 amp pulse which decays to 0 volt in approximately 300 ms. This simulator has a bank of capacitors having a capacity of about 29K .mu.F and an output impedance of about 4 ohms which discharges into a device-under-test (DUT) upon turning on a silicon controlled rectifier (SCR).
Recognizing that in the real world with modern alternators, the removal of a battery lead or when battery terminals become corroded while heavily loading an automobile alternator will generate a transient. The transient would build up in 5 to 10 ms, and rise from an alternator voltage of 13.5 volts to a high voltage level of about 105 volts With a peak current of 150-200 amperes; then decay back to the battery voltage in about 300 ms depending upon the time it takes the voltage regulator to reduce the alternator field.
As the transient rises to the 30 volt level, destruction of the vehicle lights occur; at about 60 to 80 volts, destruction of the engine control electronics and the radio occur. At other voltage levels of the transient, destruction of various other electronic devices results. Also, in the real world, intermittent worse case load dump transients sometimes appear.
Another severe transient, alternator field decay transient, produces negative pulses which occur after disconnection of the field from the battery when turning the ignition switch off. The amplitude of this transient depends upon the voltage regulator cycle at the time of shutdown and may vary from -40 to -100 volts with a duration of 200 ms.
Hence, to realistically simulate worse case transients and to develop the capability of protecting automotive devices from destruction during the various stages of the transient, a particular type of simulator which accurately reproduces the worst case alternator load dump and intermediate resistive and inductive disruption was needed. A search instituted to find such a simulator resulted in the simulator of the present invention.